Noritz tankless water heater error code 35 typically indicates a flame rod or burner combustion issue that requires checking gas supply and ventilation.
Table of Contents
- What does error code 35 mean on a Noritz tankless water heater?
- What usually causes error code 35 to appear?
- How can I safely perform quick fixes for error code 35?
- What are the next troubleshooting steps if the reset fails?
- Quick reference table for Noritz error code 35 symptoms
- When should you stop troubleshooting and call a professional?
- What information should you prepare before calling a technician?
- How can you prevent error code 35 from coming back?
What does error code 35 mean on a Noritz tankless water heater?
Error code 35 on a Noritz tankless water heater indicates a problem related to the flame sensing rod or improper flame combustion during operation.
When your water heater attempts to fire up, internal sensors check for a stable flame. If the flame rod fails to detect proper combustion or if the flame extinguishes unexpectedly, the unit locks out and displays error code 35 for safety. Because exact diagnostic nuances can vary slightly across different Noritz model series, always check your specific owner manual to confirm.
- The flame sensing rod detects whether gas is successfully burning inside the heat exchanger.
- Error code 35 stops gas flow to prevent dangerous unburned gas buildup in the unit.
- Dirty or corroded flame rods often fail to send the correct electrical signal back to the control board.
- Blocked intake or exhaust venting can starve the burner of necessary oxygen for clean combustion.
- Interrupted gas supply pressure during ignition will immediately trigger this safety lockout code.
What usually causes error code 35 to appear?
Common triggers for error code 35 include soot buildup on the flame rod, low gas supply pressure, or obstructed air intake vents.
Over time, normal operation or environmental factors can interfere with ignition reliability. Carbon deposits or scale on the flame sensor block electrical feedback. Additionally, utility supply fluctuations or spider webs inside the vent pipes can disrupt the air-to-gas ratio required for stable combustion, leading directly to this fault code.
- Carbon accumulation or oxidation coating the flame sensing rod surface.
- Inadequate gas pressure delivered from the main residential meter or regulator.
- Debris, leaves, or nests blocking the outdoor air intake or exhaust termination cap.
- Loose or disconnected wiring harness running between the flame sensor and control board.
- Faulty electronic control module failing to properly read sensor feedback signals.
How can I safely perform quick fixes for error code 35?
You can attempt to clear error code 35 by performing a simple power reset and checking your external gas supply valves.
Before trying any troubleshooting steps, make sure you understand basic safety rules. Turn off the power switch or unplug the unit before touching any internal wiring. Because this is a gas appliance, never attempt to adjust gas valves or internal gas components yourself if you smell gas or lack experience. Stop immediately and call a professional.
- Unplug the Noritz water heater power cord or switch off the dedicated circuit breaker.
- Verify that the main manual gas supply valve to the water heater is fully open.
- Wait a full sixty seconds to allow the internal computer memory to completely clear.
- Plug the unit back in or turn the circuit breaker switch back to the on position.
- Open a nearby hot water faucet to test if the burner ignites successfully without error.
What are the next troubleshooting steps if the reset fails?
Inspect the exterior vent terminals for blockages and check that all electrical connections to the flame sensor are secure.
If a simple power reset does not resolve error code 35, you need to inspect external components that affect combustion airflow and sensor communication. Always ensure the appliance is completely powered down before removing the front cabinet cover to inspect internal wiring connections or sensor plugs.
- Unplug the water heater and remove the front metal cover panel carefully.
- Locate the flame sensing rod assembly near the main burner manifold.
- Check that the wire terminal attached to the flame sensor is clean and firmly connected.
- Inspect the outdoor intake and exhaust vent pipes to remove any visible blockages.
- Reinstall the front cover securely and restore power to test appliance operation.
Quick reference table for Noritz error code 35 symptoms
Review this symptom table to match specific operational failures with their most likely causes and recommended corrections.
Different behavioral triggers can help isolate whether the issue stems from gas delivery, electrical sensing, or airflow restriction. Use this quick reference guide to compare what your water heater is doing against standard diagnostic patterns.
| Symptom | Likely cause / fix |
|---|---|
| Code appears immediately on startup | Closed gas valve / Open valve fully |
| Code appears after brief ignition | Dirty flame rod / Clean with fine sandpaper |
| Code triggers during windy weather | Vent blockage or cap issue / Clear debris |
| Intermittent code during high demand | Low gas pressure / Call gas utility |
| Unit clicks repeatedly then errors | Igniter failure / Inspect igniter gap |
When should you stop troubleshooting and call a professional?
Stop troubleshooting and call a licensed plumber or gas technician if you smell gas, suspect a gas valve failure, or if cleaning the flame sensor does not work.
Gas appliances demand strict adherence to safety protocols to prevent fire, property damage, or carbon monoxide exposure. If basic resets and external vent inspections do not clear error code 35, internal component replacement is likely required. Never attempt DIY repairs on gas valves, heat exchangers, or sealed combustion systems.
- Stop immediately and evacuate if you detect any smell of natural gas or propane.
- Call a professional if the error code returns immediately after every reset attempt.
- Contact a technician if internal burner parts show heavy corrosion or physical damage.
- Never service gas regulators, gas control valves, or sealed gas manifolds yourself.
- Hhire a certified expert for any electrical repairs involving high-voltage components.
What information should you prepare before calling a technician?
Have your exact water heater model number, serial number, warranty status, and a list of attempted troubleshooting steps ready.
Providing accurate appliance details helps service providers order the correct replacement parts before arriving at your home. You can typically find the model and serial number printed on the white data specification label affixed to the right side of the outer cabinet.
- Locate the complete model number and serial number on the side rating plate sticker.
- Check your purchase records to determine if the unit is still within the manufacturer warranty period.
- Write down the exact error code number displayed on the digital remote monitor.
- Note whether the error happens every time you turn on hot water or only intermittently.
- Keep a record of the specific troubleshooting steps you already tried performing.
How can you prevent error code 35 from coming back?
Prevent future occurrences of error code 35 by scheduling annual professional maintenance and keeping outdoor vents clear of debris.
Routine preventive maintenance extends the operating lifespan of your tankless water heater and prevents unexpected breakdowns. Keeping intake filters clean and scheduling professional burner cleanings ensures stable ignition and prevents mineral scale or soot buildup from interfering with safety sensors.
- Schedule annual maintenance with a qualified technician to inspect and clean burners.
- Inspect outdoor intake and exhaust vent terminals monthly to ensure clear airflow.
- Flush the water heater heat exchanger yearly to prevent damaging mineral scale accumulation.
- Keep the area surrounding the water heater free of dust, lint, and chemical vapors.
- Test safety shut-off features periodically according to manufacturer maintenance guidelines.
Frequently Asked Questions
Can I clean the flame sensor myself on my Noritz water heater?
Yes, homeowners comfortable with basic tools can often clean a dirty flame sensor. First turn off the power and gas supply, remove the front panel, gently scrub the metal rod with fine sandpaper or steel wool to remove carbon buildup, and reassemble carefully before testing.
What should I do if error code 35 keeps coming back after a reset?
If power resets fail to resolve the issue, the flame rod is likely too degraded or dirty, or your gas supply pressure is fluctuating. Continued recurrence means you should contact a licensed service technician to test gas pressures and inspect internal components.
Does error code 35 mean there is a gas leak in my home?
Not necessarily. Error code 35 usually means the unit failed to detect a stable flame during the ignition sequence, causing it to shut off the gas valve for safety. However, if you ever smell gas near the appliance, leave the area immediately and call emergency services.
Will flushing my water heater help clear error code 35?
Flushing the heat exchanger removes mineral scale and helps maintain overall appliance efficiency, but it does not directly fix a flame sensing or ignition error. Code 35 is specifically tied to combustion sensing, gas supply, or airflow rather than internal water scaling.
Are Noritz error codes universal across all tankless models?
Many core error codes are similar across Noritz tankless product lines, but exact definitions and troubleshooting procedures can vary by specific model year or series. Always consult your specific owner manual or the official manufacturer support page to verify.
Bottom Line
Start by performing a simple power reset and verifying that your gas supply valve is fully open. If error code 35 persists, contact a licensed professional to inspect the flame sensor and gas manifold safely.
Sources
- Noritz Owner’s Manual
- Noritz Technical Support Guide
- Manufacturer Support Page